Title: CloneSpy
Languages: English
Compatibility: Windows NT 4.0, Windows 2000, Windows XP, Windows Vista, and Windows 7 x86 (32-bit) and x64 (64-bit)
License: Freeware
Author: clonespy.com
Opinion: Used this for a long time. Very flexible -- can check for duplicates across multiple trees and automatically or prompt for deletion
Website: http://www.clonespy.com
Download: http://www.clonespy.com/?Download